1. Field of the Invention
This invention relates generally to an LED light for a vehicle and, more particularly, to a white LED headlight for a vehicle that employs chip-on-board circuit technology for electrically mounting the LEDs to a circuit board.
2. Discussion of the Related Art
Vehicle styling and appearance provides significant and important advantages for attracting customers. One recognized area that is known to enhance vehicle attraction is the appearance and design of the various vehicle lights, sometimes referred to as the vehicle's jewels, including, but not limited to, headlights, tail lights, turn signals, back-up lights, center high mounted stop lamps (CHMSLs), running lights, fog lamps, side markers, etc. In fact, modern vehicle designs pay close attention to the styling and design of the vehicle lights.
Current vehicle lights employ various types of light sources suitable for different designs and conditions. For example, vehicle lighting designs have employed incandescent lamps, neon tubes, halogen lamps, xenon lamps, etc. Some modern vehicle light designs have employed light emitting diodes (LEDs) that are able to provide various colors in an inexpensive and compact arrangement. LEDs typically do not suffer from burn-out, and have good drive characteristics, high luminance, high efficiency, high vibration resistance and durability to endure repetitive on/off operations. Therefore, LEDs have been attractive for vehicle lighting.
LEDs emit monochromatic light at wavelengths depending on the doping characteristics of the LED semiconductor material. Traditionally, the most efficient LEDs have emitted red light, green light or blue light. It has heretofore not been possible to provide an LED semiconductor material that emits white light. However, various LED designs are available that convert colored light to white light. One design employs a combination of red, green and blue LEDs arranged close together. The light from the LEDs is combined and diffused to provide the white light. However, these types of LED designs have typically been limited because of variances in tone, luminance and drive power of the different LEDs.
Another white light LED design employs a colored light LED and a fluorescent material that absorbs the colored light and emits white light. U.S. Pat. No. 6,069,440, issued May 30, 2000 to Shimizu et al., discloses a white light LED including a layer of phosphor deposited over a blue light LED. The phosphor includes a fluorescent that absorbs the blue wavelength light and emits white light. In one particular design, the LED material is InGaN and the phosphor layer includes an yttrium-aluminum-garnet fluorescent material.
There is a push in the automotive industry to develop white light LEDs so that LEDs can be used in vehicle headlights. Important design concerns for vehicle headlights come into play when using the existing technology for generating white light from LED semiconductors, such as employing blue light emitting LEDs in combination with a phosphor layer. Particularly, intensity and directional considerations are important for the tightly regulated headlight requirements. Further, providing a compact, efficient, low cost and aesthetically pleasing LED package is necessary.